1. Field of the Invention
The present invention relates to a magnetic head that merges read and write portions with vialess lead layers from a magnetoresistive (MR) sensor to exit pads and more particularly to first and second lead layers which are connected at first ends to the MR sensor and are connected at second ends to first and second exit pads wherein the first and second leads do not have any vias between the MR sensor and the first and second exit pads.
2. Description of the Related Art
A write head is typically combined with a magnetoresistive (MR) read head to form a merged MR head, certain elements of which are exposed at an air bearing surface (ABS). The write head comprises first and second pole pieces connected at a back gap recessed from the ABS. The first and second pole pieces have first and second pole tips, respectively, which terminate at the ABS. An insulation stack, which comprises a plurality of insulation layers, is sandwiched between the first and second pole pieces, and a coil layer is embedded in the insulation stack. A processing circuit is connected to the coil layer for providing write current to the coil layer which, in turn, induces magnetic fields (called "write fields") in the first and second pole pieces. A non-magnetic gap layer is sandwiched between the first and second pole tips so that write fields of the first and second pole tips at the ABS fringe across the gap layer.
In a magnetic disk drive, a magnetic disk is rotated adjacent to and a short distance (fly height) from the ABS so that the write fields magnetize the disk along circular tracks. The written circular tracks then contain magnetized segments with fields detectable by a read head.
An MR read head includes an MR sensor sandwiched between first and second non-magnetic gap layers and located at the ABS. The first and second gap layers and the MR sensor are sandwiched between first and second shield layers. In a merged MR head, one layer serves as the second shield layer and the first pole piece. The MR sensor detects magnetic fields from the circular tracks of the rotating disk by a change in resistance which corresponds to the strength of the fields. A sense current conducted through the MR sensor results in voltage changes received by the processing circuitry as readback signals. The MR sensor may be an anisotropic MR (AMR) sensor or a spin valve sensor.
One or more merged MR heads may be employed in a magnetic disk drive for reading and writing information on circular tracks of a rotating disk. A merged MR head is mounted on a slider carried on a suspension. The suspension is mounted to an actuator which rotates the magnetic head to locations corresponding to desired tracks. As the disk rotates, an air cushion is generated between the rotating disk and an air bearing surface (ABS) of the slider. The force of the air cushion against the air bearing surface is opposed by the opposite loading force of the suspension, causing the magnetic head to be suspended a slight distance (flying height) from the surface of the disk. Flying heights are typically on the order of about 0.05 .mu.m.
Magnetic heads are made in rows and columns on a wafer substrate. A full film of first shield material is deposited on the wafer, followed by patterning the full film into first shield material at each head site, which approximates the size of a trailing edge of the slider. While the description will now be addressed to making a single magnetic head at a single magnetic head site, the description applies to all of the magnetic head sites on a wafer. In the prior art, final patterning of the first shield comes in a subsequent step. A first gap is formed on the first shield material. An MR stripe of the MR sensor and a very thin initial set of leads are then formed on the first gap material, with first ends of the leads connected to the MR stripe and other films formed to complete the MR sensor. An intermediate or stitched set of leads that is recessed from the ABS is then formed on top of the initial set of leads, except over small portions of the initial set of leads adjacent the MR sensor, in order to increase conductivity for the sense current to the MR sensor. A second gap layer is then formed on the MR sensor, the leads, and the first shield layer, followed by patterning the first shield layer to a final size. This size is typically 250 .mu.m along the ABS by 100 .mu.m recessed into the head from the ABS. The second shield layer is then formed, followed by deposition of a hard baked photoresist layer that provides the first insulation layer of the insulation stack. A via is formed through the hard baked photoresist layer to second end portions of the intermediate set of leads. The first insulation layer is patterned with a via in the same location either prior to or after forming the hard baked photoresist layer. Simultaneously with forming a coil layer on the hard baked resist layer, a final set of leads is formed, extending from the via to first and second pad sites. A third lead connected to one end of the coil to a third pad site may also be formed. The via makes connection between the final set of leads and the intermediate set of leads of the read head. The remainder of the head is completed by forming one or more additional insulation layers on the coil layer, forming the second pole piece and fourth lead from the other end of the coil to a fourth pad site, forming vias at the pad sites, plating studs in the vias, forming an overcoat, and depositing gold pads that connect to the studs. This is followed by dicing the wafer into rows of heads, lapping each row of heads to form an air bearing surface, and dicing the row of heads into individual sliders, each slider having a respective magnetic head at a trailing edge thereof.
The above process requires many steps to make the leads for the read head. Since the first shield is patterned after forming the initial and intermediate set of leads, a via is required in the second insulation layer as well as the hard baked resist to connect the final set of leads to the intermediate leads. The sizes of the initial and intermediate leads dictate the size of the first shield layer, making it larger than required to shield the MR sensor. The primary purpose of the first and second shield layers is to shield the MR sensor from upstream and downstream fields along the track of the magnetic disk, so that linear resolution and bit density are promoted. For this purpose alone, the area of the first shield layer can be reduced to about 1% the size described hereinabove. This would lead to additional benefit by reducing the inductance of the write coil, permitting higher frequencies of operation and therefore higher bit throughput. In sizing the first and second shield layers, stray magnetic fields must also be taken into account. It would be desirable if the designer could design the size of the first shield layer without being constrained by sizing the first shield layer to accommodate the initial and intermediate set of leads. It would further be desirable if the number of processing steps required to form a merged head could be lessened.